
.nav .backTop{
    width: 45px;
    background: #000;
    height: 45px;
    position: fixed;
    right: 50px;
    bottom: 100px;
    display: none;
    border-radius: 50%;
    z-index: 10000;
}
.nav .backTop a{
    color: white;
    font-size: 30px;
    text-align: center;
    line-height: 45px;
    display: block;
}